[<< wikibooks] The Computer Revolution/Networks/VPN
=== Virtual Private Networks ===
A VPN is a secure pathway through a public network that is used to allow private access to an institutions network.  Many businessmen and women use this type of network to communicate with their company network securely using the internet. This communication is usually encrypted for the case that it ends up in the wrong hands. A VPN may be used to share data and give access to databases and printers.

VPN is a point-to-point connection across a private or public network, such as Internet. A VPN client uses tunneling protocols (special TCP/IP-based protocols) to make a virtual call to a virtual port on a VPN server.  Typically, a client initiates a virtual point-to-point connection to a remote access server over the Internet. The remote access server answers the call, authenticates the caller and transfers data between the VPN client and the organization’s private network. VPN protects any communication that is carried out over a public network such as the internet. They can also provide several types of data protection including: confidentiality, integrity, data origin authentication, replay protection, and access control.
Data shared across a VPN is encapsulated or wrapped with a header. The header contains routing information that enables the data to travel through the shared or public network to reach its destination. To emulate a private link, the data is encrypted for confidentiality. Packets that are intercepted on the shared or public network are indecipherable without the encryption keys.